The present invention relates to a novel cleansing composition based on oily substances, particularly for cleansing skin and/or hair, which has excellent dermatological properties.
Skin and hair can be cleansed in various ways, even with water alone. However, the use of water alone may cause swelling of the horny layer and depletion of the water-soluble constituents of the NMF (Natural Moisturizing Factor), that is, the group of water-soluble substances which are responsible for correct skin hydration. Moreover, water alone cannot remove dirt of an oily nature or any residues of a lipid nature.
For cleansing skin and hair, it is therefore usual to use either formulations based on water and surfactants, that is, molecules which, by virtue of their amphiphilic structure, are capable of removing lipid substances and keep them in aqueous solution or suspension, or formulations based on oily substances which make use of the “similia similibus solvuntur” principle. By virtue of their oily nature, these substances are in fact capable of removing sebum and hydrophobic dirt without, however, removing the water-soluble hydrating components (NMF) of the skin. This is particularly desirable when the skin or hair are irritated or damaged by environmental conditions (for example, atmospheric conditions or pollution) or physiological conditions (for example, ageing or sensitive skin).
There are many oily substances which can be used for this purpose and they may be either natural or synthetic. Amongst these are substances which are fluid at ambient temperature (oils), pasty substances (butters, fats), and solid substances (waxes). From the chemical point of view, these substances can be classified as:                hydrocarbons (paraffinic or naphthenic) such as mineral oil, vaseline, paraffin, ozocerite, ceresin;        terpenic hydrocarbons such as squalane, squalene, pristane, hexaisoprene, polyisobutylene;        siloxanic polymers such as silicones and other heterolipids, including propoxylated alcohols;        triglyceric esters such as most vegetable and some animal oils and fats (groundnut oil, karite butter, safflower oil, coconut butter, palm butter, soya oil, sunflower oil, olive oil, rice-germ oil, sweet almond oil, sesame oil, cocoa butter, wheat-germ oil, grape-seed oil, etc.); lecithin, which is a phosphatidyl cholinic glyceride, falls within this group;        non-triglyceric esters such as lanolin, beeswax, spermaceti, carnauba wax, candelilla wax, the uropygial fat of aquatic birds, and a great many synthetic esters (isopropyl myristate, which is most often used, may be mentioned by way of example);        fatty acids produced by the hydrolysis of vegetable fats (stearic acid is mainly used) of or lanolin (lanolic acids);        fatty alcohols (for example, oleyl alcohol, cetyl alcohol) sterolic alcohols (for example, cholesterol), triterpenic alcohols (for example, lanosterol); many of these alcohols form part of the non-saponifiable fraction of vegetable lipids; the group also includes synthetic alcohols such as octyl dodecanol;        essential oils, for example, essential oil of rosemary, lavender, angelica, artemisia, valerian, basil, bergamot, citronella, lemon, myrrh, patchouli, rose, or cinnamon.        
However, cleansing compositions which are based on oily substances pose considerable formulation problems which are due both to poor solubility in water and to low foaming capacity. These problems have been addressed in the prior art by the use of various surfactants capable of increasing the dispersibility of the oily substances in water, improving the rinsability of the composition, and/or increasing foam formation.
For example, patent application DE-A 29 43 202 describes the use of monoalkylamines or dialkylamines, monoalkanolamines or dialkanolamines and/or salts of alkyl/alkanolamines of fatty alcohol sulphates as surfactants.
U.S. Pat. No. 4,371,548 describes the use of a C8-C18 sulphated fatty alcohol, optionally ethoxylated, neutralized by one or more amines, in a mixture with a C8-C10 ethoxylated sulphated fatty alcohol of ammonium.
U.S. Pat. No. 5,653,988 describes the use of a mixture constituted by a fatty alcohol, optionally ethoxylated, neutralized with various amines (preferably MIPA), an ethoxylated fatty alcohol (preferably Laureth-4) and a mono/diethanol amide (preferably Cocamide DEA).
U.S. Pat. No. 6,132,738 also describes the use of TIPA Laureth Sulphate.
However, a further problem to be addressed in the formulation of cleansing compositions for skin and/or hair is that of the aggressiveness of the surfactant. In the cosmetics field, there is in fact a tendency to avoid the use of ingredients, particularly surfactants, which are irritating to skin and hair. This is even more desirable for compositions which are based on oily substances, the beneficial effects of which would be cancelled out by the presence of an aggressive surfactant in the composition. For this reason, the current tendency in the cosmetics field is to avoid the use of aggressive surfactants such as, for example, cocamide DEA—because of the possible formation of nitrosamines—and sulphated fatty alcohols, because of their aggressiveness and the dioxane content of the ethoxylated derivatives.
The present inventors have now found that the use of acylates of amino-acids, proteins and/or peptides as surfactants in the formulation of cleansing compositions based on oily substances, particularly for cleansing skin and/or hair, enables compositions having excellent dermatological properties to be produced. These compositions have in fact been found to be extremely gentle towards skin and/or hair.
Simply adding these surfactants to a conventional oily formulation can reduce its aggressiveness and increase its tolerability. These molecules may also have a corrosion-inhibiting effect on domestic pipes.